Buy my cable - 12 pin to USB. Load TunerPro RT (free version included) on your laptop and scan your engine. Look at what the MAP sensor is doing. Look at what the MAP sensor is doing when the trouble is happening and troubleshoot it.http://reddevilriver.com/aldl.html
Alternative - Run a wire to the Green wire of your MAP sensor. Figure out some way to back probe the MAP sensor that will stay solid in there. Read the voltage on your MAP sensor and watch for it to wack out. .9v ish is fine. Anytime it's jumping up like 4.5 to 5v is trouble unless you have the throttle wide open.
If the Black wire of the MAP sensor is not making a good connection it could be causing this trouble. Inspect the harness for any damage. Look near the belts.